Patent Document 1 shows an arrangement in which a water-cooled type intercooler is arranged in a serge tank of a resin made intake manifold. If, like this, an intercooler is installed to an intake manifold, a performance of a supercharger can be increased while reducing the entire volume of an air intake system.
In the water-cooled type intercooler, a plurality of metal members are combined by brazing or the like in a manner to constitute a watertight cooling water flow portion isolated from an intake air flow portion in which intake air flows. Accordingly, a mechanical strength of the brazed portions of the intercooler is lowered. Furthermore, a possible vibration applied to the intercooler tends to give adverse influence to portions where the mechanical strength is lowered. Thus, in case of installing an intercooler in a collector portion, it is preferable that the intercooler does not contact the intake manifold except the portions where the intercooler is actually fixed to the intake manifold.
Furthermore, in the resin made intake manifold, the thermal contraction of the resin tends to change depending on various conditions such as the season, weather, shape and thickness. Particularly in portions that are lowered in rigidity, variation of the deformation is increased, and thus it is difficult to correctly estimate a final shape of the resin made intake manifold.
Thus, in case of installing an intercooler in the resin made intake manifold, it is necessary to avoid interference or contact between the intercooler and the resin made intake manifold as less as possible even after the intake manifold is subjected to a deformation due to the thermal contraction and the like. For satisfying the necessity, it is necessary to set a rather large clearance between the intake manifold and the intercooler in advance.
However, the amount of intake air flowing through the clearance increases as the size of the clearance between the intake manifold and the intercooler increases, and thus, the amount of intake air that needs to flow in the intake air flow portion defined in the intercooler is reduced instead. This means that if the clearance is unnecessarily increased in size, the cooling performance of the intercooler to the intake air is lowered, which is an undesired matter.